Recovery efforts after the widespread devastation and destruction caused by superstorm Sandy could be among the most expensive in United States history.

"We are now in the recovery mode, response and recovery," Department of Homeland Security Secretary Janet Napolitano said today. "We are moving large amounts of resources into the affected areas. It will be ... if not the most extensive and expensive, one of the most in our nation's history."

Napolitano spoke about what lies ahead in the wake of Sandy at a Washington Post forum on cybersecurity issues.

After surveying the devastated New Jersey shoreline today with Gov. Chris Christie, President Obama said that while there was a lot of work to be done, the cleanup effort would be handled with "an all-hands-[on]-deck approach."

"What I can promise you is that the federal government will be working as closely as possible with the state and local officials, and we will not quit until this is done," Obama said from Brigantine, N.J., noting that states from as far away as California have pledged to send crews and equipment to the affected areas.

Obama declared parts of New Jersey, along with parts of New York, a major disaster area, which would allow federal funding for storm-related repairs.

Recovery from Hurricane Katrina in 2005 has been considered the costliest U.S. hurricane recovery, at nearly $106 billion, according to the National Hurricane Center. Hurricane Andrew in 1992 cost about $45.5 billion and Ike in 2008 cost more than $27 billion.

More than six million people are still without power across 17 states and Sandy is now being blamed for at least 61 deaths in the U.S. and two people missing, according to The Associated Press. Two million people have had power restored since Tuesday.

Napolitano said that President Obama had cancelled his campaign events over the past few days to focus on storm response efforts.

"Before it actually made landfall, we had -- and this is something we've developed over the last few years with FEMA -- pre-positioning, pre-positioning equipment, pre-positioning food and water, other things that are likely to be necessary, pre-positioning personnel, so that as the storm clears and it is safe to go back in, we can move very, very quickly." Napolitano said.

She added that "patience" would be "the watchword of the day."

Residents along the East Coast are beginning to pick up the pieces after the Sandy devastated the most densely populated region in the country, with New Jersey experiencing "unthinkable" damage to its coastline as homes were swept from their foundations and amusement park rides were washed into the ocean.

Hundreds of thousands of people who had to evacuate their homes are left wondering what -- if anything -- was left. For those residents living on the New Jersey coastline, Christie described the damage as "unfathomable" and "unthinkable."

Images from around the storm-affected areas depicted scenes reminiscent of big-budget disaster movies. In Atlantic City, N.J., a gaping hole remained where once a stretch of boardwalk sat by the sea.

"It won't be same. It will be different because many of the iconic things that made it what it was are not gone and washed into the ocean," Christie said at a Tuesday evening press conference after surveying the damage.

Christie said that he planned on speaking to Obama about getting Army Corps of Engineers into the state to begin rebuilding as soon as possible, especially the Jersey Shore.

"As a kid who was born and raised in this state and who spent a lot of time over my life, both my childhood and my adult life, at the Jersey Shore, we'll rebuild it," he said. "No question in my mind we'll rebuild it."

Seaside Heights, a city synonymous with fun, was submerged under water with destruction as far as the eye could see. Homes, cars and amusement park rides littered the coastline and the ocean.

"The boardwalk we walked on together this summer greeting residents, talking to those business owners, it's gone," Christie said.

Timothy Husar took a picture of the submerged rollercoaster in Seaside Park that went viral on social media.

Husar added that the high tides and strong winds also pushed debris from other coastline cities toward Seaside Heights.

"Throughout the ocean you see the northerly or southerly winds pushing debris that we suspect is from Atlantic City and the Wildwood area up towards our docks," he said.

Boat rescues continued along the storm-ravaged shore Tuesday night for those residents who did not heed the warnings and mandatory evacuation orders.

Tom Moriarty was taken to an Atlantic City hospital with chest pains. His daughter remained at his flooded home in Brigantine, N.J.

"She said everything was fine and that if worse comes to worse, she and her boyfriend were going to go into the attic," Moriarty said.

The number of power outages topped 1.9 million customers in New Jersey and half a million in New York City, and approached another million on New York's Long Island.

Nearly 4,000 utility workers from all areas of the country are rushing to New York to help turn on the power after much of lower Manhattan plunged into darkness and dimmed the famous skyline.

"You should not expect the vast bulk of those people that do not have service today to get service much before the weekend," Mayor Michael Bloomberg said during a Tuesday news conference.

All bridges and tunnels have reopened, with the Holland Tunnel and Brooklyn-Battery Tunnel the only exceptions.
Officials hoped to have power restored to New York in two to three days and aimed to have the subways running by the weekend, Bloomberg said.

Faced with the chance of not having power for days, looting has become a problem in the Coney Island section of Brooklyn, N.Y., Tuesday night.

More than 100 police officers stood on corners or cruised in cars to guard a strip of vandalized stores and a damaged bank, to the relief of shaken residents.

"We're feeling OK, but at first we felt worried," 12-year-old Oleg Kharitmov told The Associated Press as he walked his dog with his parents by the bank. "I'm pretty happy that the cops are here."

New York City schools remained closed for a third straight day as limited bus service resumed Tuesday night. The New York Stock Exchange reopened today, after an unprecedented two-day shutdown, with Bloomberg ringing the opening bell.

John F. Kennedy Airport and Newark Liberty International Airport reopened at 7 a.m. this morning. LaGuardia Airport remained closed after extreme flooding to the runways, but planned to reopen on a limited schedule Thursday at 7 a.m.

Bloomberg encouraged parents and children to enjoy Halloween but to use "good judgment and be careful." The annual Halloween parade in Manhattan's West Village was postponed for the first time in 39 years.

In New Jersey, Halloween has taken a back seat to the recovery effort and towns were being ordered to reschedule any festivities associated with the holiday.

"It's just not safe enough for kids to go around, but I don't want kids to be disappointed and so tomorrow we will reset Halloween by executive order," Christie said Tuesday.

The annual NYC Marathon -- which attracts runners from all over the world -- plans to go on as scheduled Sunday, but with the subways still down and airports resuming with limited service, it could be difficult for all expected runners to make it to the starting line.